Delta-sigma modulation is an example of a technique for generating a 1-bit pulse train representing an analog waveform.
The delta-sigma modulation is a kind of oversampling modulation. A delta-sigma modulator includes a loop filter and a quantizer. The quantizer is able to output a 1-bit pulse train as a quantized signal.
The 1-bit pulse train outputted from the delta-sigma modulator is restored to the original analog waveform by simply passing through an analog filter. That is, the 1-bit pulse train outputted from the delta-sigma modulator is a digital signal, but represents an analog waveform, and therefore has both the property as a digital signal and the property as an analog signal.
It is conceivable to transmit an analog signal as a digital signal by utilizing the 1-bit pulse train having the aforementioned properties. In this case, however, degradation in signal characteristics of the analog signal due to utilization of the 1-bit pulse train has become a problem.
The inventors of the present invention have discovered that, in the 1-bit pulse train also having the property as an analog signal, asymmetry between a pulse rising waveform and a pulse falling waveform causes degradation in signal characteristics as the analog signal (refer to Patent Literature 1).
That is, if a distortion component (asymmetric component) that is included in the waveform of the 1-bit pulse train and causes asymmetry between the pulse rising waveform and the pulse falling waveform is suppressed, degradation in signal characteristics as the analog signal represented by the 1-bit pulse train can be suppressed.